The present invention relates to a composting accelerator; a process for producing, by using said composting accelerator, an organic fertilizer by composting a raw material to be composted; an organic fertilizer available by this process; and a method for spreading the composting accelerator on the floor of a livestock barn. More specifically, this invention pertains to a composting accelerator capable of composting an organic raw material to be composted, such as livestock excrement, food remnants, activated sludge and ligneous residues, while reducing an emission amount or emission time of ammonia, thereby producing a good-quality organic fertilizer having excellent fertilizing efficiency in a short period; a process for producing an organic fertilizer by using said composting accelerator; and a method for reducing a malodor such as ammonia odor by spreading said composting accelerator on the floor of a livestock barn.
Although conventional, popularly-employed compound fertilizers are fast acting, they have caused problems such as poor growth or death due to a concentration disturbance, soil infertility due to continuous use, and environmental pollution. In recent years, therefore, a compost prepared by composting an organic raw material to be composted, for example, animal excrement such as fowl dung, swine dung or cattle dung, food remnants dumped from home or food plants, or activated sludge has been sprayed to the soil, whereby the above-described problems of the compound fertilizer can be overcome and plants can be reared while the soil fertility is reinforced. Although the above-described organic raw material to be composted can be composted singly without addition of any composting accelerator or composting auxiliary, composting does not proceed smoothly because of a large water content and poor air permeability. It is therefore common to carry out composting after mixing a raw material to be composted with a plant type organic matter such as sawdust, wheat straw, rice straw and/or fallen leaves, and adjusting the water content of the resulting mixture. It however takes time to decompose the plant type organic matter such as sawdust because it contains a sparingly decomposable component in a large amount. Composting of a raw material to be composted with the plant type organic matter incorporated therein is accompanied with the drawback that it takes long time (usually, 3 to 6 months) for composting the mixture and in some cases, the mixture becomes anaerobic during a long composting period, thereby emitting an offensive odor over a long period of time. In addition, a lignin component contained in the plant type organic matter is decomposed into a phenolic acidic substance, which happens to inhibit the growth of a plant.
Also known is a process for composting an organic raw material to be composted such as livestock excrement, food remnants or activated sludge after adjusting its C/N ratio, water content and pH by using a so-called xe2x80x9creturned compostxe2x80x9d which is a fully-composted compost returned to the raw material for further composting thereof, or a mineral such as vermiculite or diatomaceous earth. Compared with the above-described process wherein a plant-type organic matter is added, this process usually produces a good-quality compost, since it does not take so much time for composting and-a phenolic acidic substance is formed in a reduced amount. It is however accompanied with the drawbacks that it takes not so long time but still takes 1 to 2 months for composting, adjustment of a C/N ratio, water content and pH of the raw material to be composted necessary for this process is cumbersome and requires much labor, and ammonia is emitted over a long period of time.
In addition, proposed is a process (Japanese Patent Publication No. Hei 5-73718) for composting an organic waste, by mixing the organic waste with artificial calcium particulate selected from tobermorite or xonotlite, compulsorily bringing the resulting mixture into contact with air to convert it into the composted material in half maturity, and naturally composting it into the composted material in full maturity. This process however requires forced composting by using a forced composting apparatus equipped with a porous plate or agitating blade for blowing the air into the mixture of the organic waste and artificial calcium silicate, so that it is complex in both step and apparatus and requires much labor and cost. In addition, artificial calcium silicate in an amount as large as 30 to 50 kg must usually be mixed with 100 kg of the organic waste for adjusting the water content of the resulting mixture to 50 to 60 wt. % upon composting, which makes a large burden in cost and labor. Moreover, artificial calcium silicate remains in the resulting compost without being decomposed and lowers a decreasing rate of the volume or weight of the organic waste, one of the important targets of the composting, whereby a smooth reduction in the amount of the organic waste is disturbed.
The organic raw material to be composted such as livestock excrement, food remnants or activated sludge has a large water content, and has an unstable pH due to various components mixed therein. The microorganism flora (microflora) contained in it therefore tends to become ill-balanced, which disturbs the proliferation of an effective microorganism group usefully acting on composting. Particularly in winter, composting of it does not proceed smoothly at a low atmospheric temperature and it requires a longer period for composting.
With the foregoing in view, the present inventors previously developed and proposed a composting accelerator comprising 100 parts by weight of an organic matter, such as wheat bran, having an arabinoxylan content of 20 wt. % or greater, 1 to 3 parts by weight of slaked lime, 3 to 10 parts by weight of a humic acid and 5 to 20 parts by weight of a microorganism material; and a process for producing an organic fertilizer by using the composting accelerator (Japanese Patent Application Laid-Open No. Hei 8-198694). Moreover, the present inventors developed and applied, for patent, a process for producing an organic fertilizer by adjusting the water content, pH and C/N ratio of a raw material to be composted which is composed of livestock excrement and/or activated sludge, to 55 to 65 wt. %, 70 to 8.5 and 20 or less, respectively, and adding, to 100 parts by weight of the thus-adjusted raw material, 25 to 50 parts by weight of a composting auxiliary composed of wheat bran, as a main component, slaked lime and the like, thereby composting the raw material (Japanese Patent Application Laid-Open No. Hei 9-48685).
The above-described inventions by the present inventors are advantageous in that the organic raw material to be composted, which has a large water content, such as livestock excrement, food remnants and activated sludge can be composted in a short time, compared with the conventional process. Based on these inventions, the present inventors have proceeded with an investigation. As a result, it has been found that there is a room for improvement in the former invention, because the pH of the composting accelerator becomes as high as 9 or greater, usually about 10 owing to a comparatively large amount of slaked lime in the composting accelerator, which induces emission of a large amount of ammonia causing a malodor. It has also been found that there is also a room for improvement in the latter invention because it needs extra time and cost for adjusting the water content, pH and C/N ratio of the organic raw material to be composted.
In a livestock barn wherein animals such as cattle, swine and horses are bred, an offensive odor due to their excrement is strong, which markedly deteriorates their breeding environment. With a view to suppressing the emission of a malodor, a microorganism material has conventionally been spread on the floor of a livestock barn. From the viewpoints of suppression of emission of an offensive odor and safety for livestock and persons working in the barn, however, a satisfactory solution for the above-described problem has not yet proposed.
An object of the present invention is therefore to provide a composting accelerator which can compost an organic waste matter such as livestock excrement from animals in a livestock barn, food remnants dumped from food industry or home, or activated sludge generated after aeration of the industrial waste in an oxidizing tank or generated from sewage treatment in a time shorter than that of the conventional accelerator while reducing an emission amount or period of ammonia compared with the conventional composting process, thereby converting it into a good-quality organic fertilizer having excellent fertilizing efficiency.
Another object of the present invention is to provide a process for composting a raw material to be composted such as livestock excrement, food remnants or activated sludge, while reducing an emission amount or period of ammonia, thereby producing, in a short time, an organic fertilizer having a high fertilizing efficiency.
A further object of the present invention is to provide a method for improving the breeding environment of livestock by effectively reducing an offensive odor emitted from its excrement in a barn while securing the safety for livestock or working person.
A still further object of the present invention is to provide a process for composting an organic waste matter such as livestock excrement discharged from animals in a livestock barn, food remnants dumped from food industry or home, or activated sludge generated after aeration of the industrial waste in an oxidizing tank or generated from sewage treatment in a short time by a simple step and operation without using any special apparatus for continuously bringing it into contact with the air, without adding slaked lime, and without conducting any special adjustment of the water content, pH and C/N ratio of the raw material to be composted, thereby converting it into a good-quality organic fertilizer having excellent fertilizing efficiency; and a composting accelerator for the process.
Disclosure of the Invention
With a view to attaining the above-descried objects, the present inventors have proceeded with an investigation. As a result, it has been found that a composting accelerator, which is available by adding heat-resistant bacteria for assimilating an organic material to an organic matter having an arabinoxylan content of 10 wt. % or greater and has pH adjusted to 6.0 to 8.5, is markedly effective for composting acceleration of an organic raw material to be composted, such as livestock excrement, food remnants or active sludge, having a high water content and that only by the addition of it to the raw material to be composted at a predetermined ratio, a good-quality organic fertilizer having excellent fertilizing efficacy can be produced very easily in a short time, while reducing the emission amount and period of ammonia, even without adjusting the water content, pH and C/N ratio of the raw material to be composted.
It has also been found that the spreading of the above-described composting accelerator on the floor of a livestock barn suppresses the emission of ammonia, which is a cause for offensive odor, and is extremely effective for the improvement of the breeding environment of livestock and that the accelerator is highly safe for animals and also persons working in the barn, because it does not contain any harmful component.
It has also been uncovered that when an organic matter having an arabinoxylan content of 10 wt. % or greater and calcium silicate are added, each at a specific ratio, to an organic raw material to be composted such as livestock excrement, food remnants, activated sludge or ligneous residues to compost the same, a good-quality organic fertilizer having excellent fertilizing efficacy is available by a markedly simple step and operation in a short time even without any special apparatus for bringing the raw material into constant contact with the air, without using slaked lime, or without any adjustment of the water content, pH and CN ratio of the raw material to be composted, leading to the completion of the present invention.
In the present invention, there is thus provided:
(1) a composting accelerator which comprises an organic matter having an arabinoxylan content of 10 wt. % or greater and heat-resistant bacteria for assimilating an organic material, and has a pH adjusted to 6.0 to 8.5.
The present invention embraces, as preferred embodiments,:
(2) the composting accelerator described above in (1) wherein the component (A) is wheat bran and/or low-grade flour powder,
(3) the composting accelerator described above in (1) for (2), which contains the component (A) in an amount of 60 wt. % or greater based on the total weight of the composting accelerator,
(4) the composting accelerator described above in any one of (1) to (3), wherein the heat resistant bacteria (B) is able to survive at 55xc2x0 C. after treated at 80xc2x0 C. for 10 minutes,
(5) the composting accelerator described above in any one of (1) to (5), wherein the heat-resistant bacteria (B) are contained in an amount of 105 CFU or greater per g of the composting accelerator, and
(6) the composting accelerator described above in any one of (1) to (5), further comprising a humic acid in an amount of 2.5 wt. % or less based on the total weight of the composting accelerator.
(7) In another aspect of the present invention, there is also provided a process for producing an organic fertilizer, which comprises adding, to 100 parts by weight (in terms of a dry matter) of a raw material to be composted, the fertilizer described above in any one of (1) to (6) so that the amount of the wheat bran and/or low-grade flour powder in the composting accelerator will become 0.2 to 25 parts by weight (in terms of a dry matter), thereby composting the raw material.
(8) The present invention also provides an organic fertilizer available by the process described in (7).
(9) The present invention also provides a method for spreading the composting accelerator described above in any one of (1) to (6) on the floor of a livestock barn.
(10) The present invention also provides a method for spreading the organic fertilizer described above in (8) on the floor of a livestock barn.
In a further aspect of the present invention, there is also provided:
(11) a process for producing an organic fertilizer which comprises adding (A) an organic matter having an arabinoxylan content of 10 wt. % or greater and (C) calcium silicate to a raw material to be composted at a weight ratio of (A):(C) ranging from 50:50 to 95:5, thereby composting the raw material.
The present invention embraces, as a preferred embodiment,
(12) the process described above in (11), wherein the component (A) and the component (C) are added in a total amount of 0.5 to 20 parts by weight based on 100 parts by weight of the raw material to be composted.
In a still further aspect of the present invention, there is also provided:
(13) an organic fertilizer produced by the above-described process (11) or (12), and
(14) a composting accelerator comprising a mixture obtained by mixing (A) an organic matter having an arabinoxylan content of 10 wt. % or greater and (C) calcium silicate at a weight ratio of (A):(C) ranging from 50:50 to 95:5.
Any organic matter having an arabinoxylan content of 10 wt. % or greater can be used as the organic matter (A) in the present invention. That having an arabinoxylan content of 20 wt. % or greater is preferred. When an organic matter having an arabinoxylan content less than 10 wt. % is used, smooth composting of the raw material to be composted into the corresponding compost in a short time cannot be attained. Specific examples of the organic matter (A) used preferably in the present invention include wheat bran (an arabinoxylan content: usually about 25 to 40 wt. %), low-grade flour powder (ditto: about 15 to 25 wt. %), rice bran (ditto: about 20 to 45 wt. %), gluten feed (ditto: 20 to 40 wt. %), beer bran (ditto: about 20 to 40 wt. %) and corn husk (ditto: about 25 to 45 wt. %). They may be used either singly or in combination.
A description will next be made of the use of the organic substance (A) and heat-resistant bacteria (B) in combination (which will hereinafter be called xe2x80x9ccomposting accelerator (AB)xe2x80x9d).
In the composting accelerator (AB), use of wheat bran and/or lower-grade flour powder as the organic matter (A) is preferred.
Wheat bran is, as you known, a protective seed coat of the wheat kernel, while low-grade flour powder contains the endosperm (wheat flour) attached to the protective seed coat of the wheat kernel and wheat bran. Each of them is available as a by-product in wheat milling. The wheat bran and low-grade flour powder each has higher proliferating action of an arabinoxylan decomposable microorganism than rice bran, gluten field or the like, because it is presumed that the wheat flour or low-grade flour powder has a C/N ratio of about 15, has a low water content (15 wt. % or lower) and has a shape which facilitates formation of voids when deposited.
The composting accelerator (AB) of the present invention may contain either one or both of the wheat bran and low-grade flour powder.
It is preferred that the composting accelerator (AB) of the present invention contains wheat bran and/or low-grade flour powder in an amount of 60 wt. % or greater (total amount when both of the wheat bran and low-grade flour powder are incorporated) based on the total weight of the composting accelerator, with 80 wt. % or greater being more preferred. Contents of the wheat bran and/or low-grade flour powder less than 60 wt. % make it difficult to prepare a composting accelerator having excellent composting accelerating effects and ammonia emission inhibitory effects.
The composting accelerator (AB) of the present invention further contains heat-resistant bacteria for assimilating an organic material.
As the heat-resistant bacteria, those capable of assimilating the above-described organic matter composed mainly of wheat bran and/or low-grade flour powder or organic raw material to be composted and surviving at 55xc2x0 C. even after treated at 80xc2x0 C. for 10 minutes. Examples of such heat-resistant bacteria include microorganisms belonging to the genus Bacillus such as Bacillus subtilis, Bacillus cereus, Bacillus coagulans and Bacillus stearothermophilus, thermophylic genus Actinomyces such as Thermoactinomyces vulgaris and Thermomonospora curvara and thermophylic mold such as Humicola insokens and Talaromyces dupontii. The composting accelerator (AB) according to the present invention can contain at least one of these heat-resistant bacteria. As the-heat-resistant bacteria for the composting accelerator (AB) of the present invention, commercially available one as a microorganism preparation may be used as is, or in some cases, the above-described heat-resistant bacteria may be used after culturing and proliferation. Many of these heat-resistant bacteria has high capacity of degrading wheat bran or low-grade flour powder and at the same time, has excellent capacity of decomposing an organic waste matter at high temperatures.
Since the composting accelerator (AB) of the present invention is capable of efficiently composting a raw material to be composted such as livestock excrement, food remnants or activated sludge while suppressing the emission of ammonia, thereby converting it into a good-quality organic fertilizer excellent in fertilizing efficiency in a short time and in addition, it is capable of effectively suppressing the emission of ammonia when spread on the floor of a livestock barn, it preferably contains the above-described heat-resistant bacteria in an amount of 105 CFU (colony forming unit) or greater per g of it, with an amount of 106 CFU or greater being more preferred.
The CFU of the heat-resistant bacteria in the present invention means the number of colonies formed when the composting accelerator is cultured on a standard agar medium for 48 hours in a thermostat of 55xc2x0 C., which will be described more specifically later in Examples.
The composting accelerator (AB) of the present invention is required to have a pH adjusted within a range of from 6.0 to 8.5, with a range of from 7.0 to 8.0 being more preferred. When the composting accelerator (AB) has pH less than 6.0, such a low pH prevents the heat-resistant bacteria from exhibiting sufficient activity upon production of an organic fertilizer by mixing the composting accelerator (AB) with a raw material to be composted so that an organic fertilizer of good quality cannot be produced in a short time and in addition, upon production of the organic fertilizer or spreading to a livestock barn, it has only low inhibitory action against the emission of ammonia and does not exhibit sufficient offensive odor preventive effects. When the pH of the composting accelerator (AB) is greater than 8.5, on the other hand, it induces an increase in the emission amount or period of ammonia upon production of an organic fertilizer by mixing of the composting accelerator (AB) with a raw material to be composted, leading to a deterioration in the production environment of the organic, fertilizer due to an offensive odor, which prevents the production of an organic fertilizer of good quality in a short time. In addition, the spreading of the composting accelerator having a pH exceeding 8.5 to a livestock barn causes a deterioration in its environment by an increase in the emission amount or period of ammonia.
Wheat bran or low-grade flour powder generally has a pH of about 6.5 so that the composting accelerator (AB) of the present invention having a pH of about 6.5 can be produced easily by mixing the wheat bran and/or low-grade flour powder with the above-described heat resistant bacteria. The pH of the composting accelerator (AB) of the present invention can be made greater than 6.5 but not greater than 8.5 (when the pH is adjusted to a particularly preferable range of from 7.0 to 8.0) only by adding an isalkaline substance in an amount enough for providing a predetermined pH value. Any alkaline substance can be used for the above-described purpose insofar as it does not have toxicity. For example, lime and slaked lime which are relatively strong alkaline, and calcium carbonate and aluminum oxide powder (ALC powder) which are weak alkaline are preferred from the viewpoints of easy pH adjustment of the composting accelerator (AB) within the above-described range and low cost. It should however be noted that when the alkaline substance is added in excess, the pH of the composting accelerator (AB) exceeds 8.5 and the target composting accelerator does not become available. Upon addition, a weakly alkaline one is preferred, because it is difficult to adjust the pH of the relatively strong alkaline substance, such as lime, added in only a small amount and it sometimes reacts with another substance.
The composting accelerator (AB) of the present invention preferably contains a humic acid in an amount not greater than 2.5 wt. % based on the total weight of the 5 composting accelerator, with an amount of 1.0 to 2.0 wt. % being more preferred. The composting accelerator (AB) containing a humic acid in the above-described amount is able to accelerate proliferation of a microorganism useful for the composting of a raw material to be composted such as livestock excrement, food remnants or activated sludge, or livestock excrement in a livestock barn, which makes it possible to produce, in a short time, an organic fertilizer having a high fertilizing efficiency and at the same time, to suppress an emission amount or period of ammonia upon production of the organic fertilizer or spreading of the composting accelerator of the present invention to a livestock barn. When the amount of the humic acid contained in the composting accelerator (AB) exceeds 2.5 wt. %, the organic fertilizer available by adding the composting accelerator (AB) to the raw material to be composted, thereby composting the latter tends to have reduced fertilizing efficiency.
Examples of the humic acid include alkali-soluble, amorphous polymeric organic acids contained in the young coal such as lignite or peat having a low coalification degree, and nitrohumic acids available by oxidative destruction of the amorphous polymeric organic acid with nitric acid and salts of the nitrohumic acids. For the composting accelerator (AB) of the present invention, a substance containing a humic acid, for example, young coal such as peat or lignite may be used instead of the humic acid. Rather than use of a young coal such as peat or lignite, use of a humic acid separated therefrom or nitrohumic acid or salt thereof is preferred, because in the latter case, small-amount addition is sufficient for proliferation of a microorganism useful for composting.
The composting accelerator (AB) of the present invention may contain another component as needed in an amount of 40 wt. % or less, preferably 20 wt. % or less insofar as it has a pH maintained within a range of 6.0 to 8.5. Examples include minerals such as vermiculite, pearlite, zeolite and diatomaceous earth; and organic materials, other than wheat bran or low-grade flour powder, such as rice bran, corn husk, sawdust and bark.
There is no particular limitation imposed on the production process of the composting accelerator (AB) of the present invention insofar as it permits uniform mixing of wheat bran and/or low-grade flour powder and heat-resistant bacteria for assimilating an organic material, and optionally a humic acid and/or another component. It can be produced easily only by mixing the above-described components at room temperature. The resulting mixture can also be formed into pellets.
Upon production of an organic fertilizer by using the composting accelerator (AB) of the present invention, it is necessary to add it in such an amount that the amount of wheat bran and/or low-grade flour powder will fall within a range of from 0.2 to 25 parts by weight (in terms of a dry matter), preferably a range of from 1.0 to 20 parts by weight (in terms of a dry matter) (in total when both the wheat bran and low-grade flour powder are contained) based on 100 parts by weight (in terms of a dry matter) of a raw material to be composted.
When the amount of the composting accelerator (AB) does not satisfy the above-described range, that is, less than 0.2 part by weight or exceeding 25 parts by weight in terms of the amount of wheat bran and/or low-grade flour powder, the composting of the raw material to be composted is not accelerated, a long period of time must be spent for composting and an increase in the emission amount or period of ammonia occurs.
There is no particular limitation imposed on the nature of the raw material to be composted upon production of an organic fertilizer by using the composting accelerator (AB) of the present invention insofar as it is a raw material for an organic fertilizer which can be composted. Examples include livestock excrement, food remnants, activated sludge and ligneous residues. The composting accelerator according to the present invention is particularly effective for the composting of an organic waste matter such as livestock excrement, food remnants or activated sludge which has been regarded as a matter difficult to treat because of a high water content and a large amount of a malodor.
There is no particular limitation imposed on the composting conditions upon production of an organic fertilizer. It is possible to produce an organic fertilizer having high fertilizing efficiency and excellent quality smoothly in a short time (usually, about 15 to 20 days), while reducing an emission amount or period of ammonia, by adding the composting accelerator (AB) to the raw material to be composted in the above-described amount, uniformly mixing them, and composting the resulting mixture while keeping aerobic conditions by intermittent stirring (cutting and mixing). The above-described stirring about once a week is usually sufficient for the production of the organic fertilizer.
Since the emission amount of ammonia lowers markedly when the content of ammonia in the composted material becomes 50 ppm or less, it is recommended to terminate the composting at the time when the content of ammonia in the composted material becomes 50 ppm or less. The composted material (organic fertilizer) having an ammonia content not greater than 50 ppm has markedly high fertilizing efficiency for plants. For example, use of such a material heightens the growth degree of Brassica Rapa var. pervidis. (a kind of Chinese cabbage) to 4 or greater, which will be described later in Examples.
The organic fertilizer available by the above-described composting has a reduced offensive or foreign odor, the decomposition of a large portion of the raw material to be composted has proceeded well and it is in the fine granular form so that it is excellent in handling properties and is useful as a fertilizer for vegetables, cereal grain plants typified by rice or wheat, or plants such as flouring plants, fruit trees or trees. In some cases, this organic fertilizer can be spread on the floor of a livestock barn and reused as a bedding material, which brings about a cost reduction of the bedding material.
The composting accelerator (AB) of the present invention may be spread on the floor of a livestock barn in a conventional manner without using any extra spreader or spreading method. Since the composting accelerator (AB) of the present invention is free of any harmful substance and is therefore excellent in safety, it may be spread on the floor of a livestock barn irrespective of the presence of animals in the livestock barn. Although the amount of the composting accelerator (AB) to be spread depends on the amount of the excrement and bedding material such as straw or sawdust in the livestock barn, it is preferably spread in an amount so that the amount of the wheat bran and/or low-grade flour powder in the composting accelerator will become 0.2 to 25 parts by weight (in terms of a dry matter) (in a total amount when both of the wheat bran and low-grade flour powder are contained) based on 100 parts by weight in total of the organic matters such as excrement and bedding material in the livestock barn. Spreading of the composting accelerator (AB) reduces emission of ammonia, thereby reducing an offensive odor in a livestock barn, whereby the environment in the livestock barn can be improved.
A description will next be made of a composting accelerator having the organic matter (A) and calcium silicate (C) used in combination (which accelerator will hereinafter be called xe2x80x9ccomposting accelerator (AC)xe2x80x9d.
In the present invention, preferably used as calcium silicate (C) is porous calcium silicate available by mixing a siliceous raw material such as silica with a calcareous raw material such as lime or cement to prepare an aqueous slurry and then curing the resulting aqueous slurry with high-pressure and high-temperature steam. Examples of such porous calcium silicate include powdery ALC (light-weight aggregate concrete), tobermorite and xonotlite. In the present invention, these calcium silicates may be used either singly or in combination.
Upon composting of a raw material to be composted, it is necessary to use an organic matter (A) having an arabinoxylan content of 10 wt. % or greater and calcium silicate (C) at a weight ratio of (A):(C) ranging form 50:50 to 95:5, preferably from 60:40 to 80:20.
When the using amount of the organic matter (A) is less than 50 wt. % [in other words, the using amount of calcium silicate (C) exceeds 50 wt. %], or exceeds 95 wt. % [in other words, using amount of calcium silicate (C) is less than 5 wt. %], each based on the total weight of the organic matter (A) and calcium silicate (C), the composting temperature does not reach the temperature (usually, 30 to 50xc2x0 C.) effective for composting of the raw material to be composted, resulting in difficulty in composting or it takes long time for composting.
Insofar as the organic matter (A) and calcium silicate (C) are used at a weight ratio within the above-described range of from 50:50 to 95:5, composting may be conducted by either one of the following processes:
(i) a composting process which comprises mixing the organic matter (A) with calcium silicate (C) at the above-described ratio in advance to prepare a pre-mixture, adding the resulting pre-mixture to a raw material to be composted and then mixing these components uniformly; and
(ii) a composting process which comprises seperately adding the organic matter (A) and calcium silicate (C) to a raw material to be composted and then mixing these components thoroughly.
The 50:50 to 95:5 pre-mixture of the organic matter (A) and calcium silicate (C) employed in the above-described process (i) can be stored or put on the market as a composting accelerator as is. Only by adding this pre-mixture, which serves as a composting accelerator (AC), to a raw material to be composted such as livestock excrement, food remnants, activated sludge or ligneous residues and mixing them uniformly, composting proceeds smoothly, whereby the raw material to be composted is composted in a short time and an organic fertilizer having excellent fertilizing efficiency can be prepared very easily in a short time.
Upon composting of the raw material to be composted, the organic matter (A) and calcium silicate (C) are added in a total amount of 0.5 to 20 parts by weight, preferably 5 to 10 parts by weight, based on 100 parts by weight of the raw material to be composted (which has not been subjected to an extra drying treatment and therefore still contains water). With regards to the dry weight of the raw material to be composted, the organic matter (A) and calcium silicate (C) are preferably added in a total amount of 1 to 100 parts by weight, more preferably 5 to 20 parts by weight, each based on 100 parts by weight of the raw material to be composted (in terms of a dry matter).
There is no particular limitation imposed on the composting conditions upon production of an organic fertilizer. An organic fertilizer having excellent fertilizing efficiency and high quality can be produced smoothly in a short time (usually, about 15 to 30 days) by uniformly adding the organic matter (A) and calcium silicate (C) to a raw material to be composted in the above-described weight ratio, uniformly mixing them, and composting the resulting mixture while keeping aerobic conditions by intermittent stirring (cutting and mixing). The above-described stirring (cutting and mixing) about once in 5 to 7 days is sufficient for the production of the organic fertilizer.
Since the organic fertilizer available by the above-described composting has a reduced offensive or foreign odor, composting of a large portion of the raw material to be composted has proceeded well and it is in the fine granular form, it is excellent in handling properties and is useful as a fertilizer for vegetables, cereal grain plants typified by rice or wheat, or plants such as flouring plants, fruit trees or trees.